North Korea said on Wednesday it successfully detonated its first hydrogen bomb, a claim that if confirmed would signal a major advancement in the isolated country's nuclear capabilities.
The announcement - made a month after North Korean leader Kim Jong-un suggested the secretive Northeast Asian nation had the capacity to launch an H-bomb - sparked immediate regional tensions and drew international condemnation.
Yet, some officials and analysts raised doubts whether the explosion was indeed a full-fledged test of a hydrogen device.
Al Jazeera examines the most important questions surrounding North Korea's announcement.
|Has North Korea actually detonated a hydrogen bomb?
People in the capital Pyongyang cheered their country's claimed military success on Wednesday, images showed, but it could be a long time before it has actually been proved a hydrogen device was indeed tested.
H-bombs are much more difficult to design and produce compared to atomic bombs - and can be thousands of times more powerful.
"Such a device could evaporate the entire city of New York completely - no one would stay alive," Andrei Lankov, a professor of Korean Studies at Kookmin University in Seoul, told Al Jazeera. "With an atomic bomb you can kill half of Manhattan, at most."
While much more potent, H-bombs are also much more costly.
"For the North Koreans to have such a powerful and expensive [device] is a bit of overkill - it simply does not make sense," Lankov told Al Jazeera.
"It's like buying a Porsche to go shopping in a shop nearby... It's a very expensive programme which will not really make a major contribution towards their security - but governments sometimes do crazy things. I'm sceptical but it might be the case."
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Adam Cathcart, a lecturer in Chinese history at the University of Leeds, said North Korea has previously made claims over huge scientific leaps that have not been substantiated.
"However, Kim Jong-un's statement back on December 10 about the state's H-bomb abilities certainly telegraphed this test, and at least tells us that the supreme leader has staked his prestige on the claim," he told Al Jazeera.
|Does the announcement change what we know about its nuclear programme?
From 2006 to 2013, North Korea conducted three nuclear tests of atomic weapons - all at the Punggye-ri site, near which a 5.1 magnitude earthquake was detected on Wednesday.
Regardless of the validity of the hydrogen bomb claims, Wednesday's announcement has left no doubt about Pyongyang's commitment to its nuclear programme, analysts said.
"[It is showing] that it's relatively successful and making progress," Remco Breuker, a professor of Korean Studies at Leiden University, told Al Jazeera. "And more importantly perhaps that the possession of nuclear weapons is non-negotiable for this regime."
"What's important is to know it [the nuclear programme] exists. When North Koreans began to talk about their nuclear programme initially there were some people who suspected that they were bluffing."
|Why did North Korea decide to do this now?
From the moment the H-bomb test was announced on state television, speculation has been rife about what prompted North Korea's action.
Some analysts said although they were not completely surprised by the move, there are still questions over its timing. In recent months North Korea appeared to have had increased its efforts to improve relations with several other countries, from its traditional regional ally China to Russia and nations in Southeast Asia.
| How does hydrogen bomb work?
"They were very unusually active and they were looking for some kind of breakthrough, some kind of improvement," said Lankov. "For a brief while, especially over the last three months, they were more open to the world about getting some investment."
Breuker said one theory is that in the absence of international tensions, the test was prompted by domestic factors, "over which we don't have any control, not even much understanding, so this is not a good situation to be in".
North Korea's government said it deserves to possess nuclear weapons to counter threats from the US, but Cathcart said he did not believe Pyongyang's latest actions were about negotiating with the Barack Obama administration - "even though in the past two decades or so, North Korea has done its most rapid negotiating with 'lame duck' US administrations in their second term".
|What's next for North Korea, its neighbours, and international relations?
Neighbouring countries and global powers issued stern statements against North Korea following Wednesday's announcement, while the UN Security Council called an emergency meeting.
While it is almost certain the move will prompt the imposing of further economic sanctions, some analysts said the measures will not have major repercussions unless the US decided to introduce comprehensive financial sanctions that would essentially ban all global banking institutions from dealing with Pyongyang.
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The test is also expected to worsen North Korea's relations with Beijing, which has long been frustrated by the nuclear programme of its troublesome neighbour, a recipient of Chinese aid and investment.
"North Korea risks losing yet more goodwill from its main patron and nominal ally - China," said Cathcart.
"I don't think that Beijing is going to abandon North Korea at the UN when it comes to human rights issues, but there will be more pressure within Chinese society and the political-diplomatic field to turn the screws on North Korea - even as China tries to keep one hand open for North Korean economic reform and external investment, which it sees as the long-term solution to the problem."
| North Korea raises alarm with nuclear test announcement
Source: Al Jazeera